Process for the coating of textiles

ABSTRACT

The present invention relates to a process for the production of coated textiles in which a textile substrate is firstly brought into contact with an aqueous dispersion comprising at least one inorganic salt and at least one modified cellulose.

The present invention relates to a process for the production of coatedtextiles in which a textile substrate is firstly brought into contactwith an aqueous dispersion comprising at least one inorganic salt and atleast one modified cellulose.

The production of synthetic leather by coating textiles with plasticshas been known for some time. Synthetic leathers are employed, interalia, as shoe upper materials, for articles of clothing, as bag-makingmaterial or in the upholstery sector, for example. Besides otherplastics, such as PVC, the main coating material used here ispolyurethane. The generally known principles of coating textiles withpolyurethane are described in W. Schröer, Textilveredlung [TextileFinishing] 1987, 22 (12), 459-467. A description of the coagulationprocess is additionally found in “New Materials Permeable to WaterVapor”, Harro Träubel, Springer Verlag, Berlin, Heidelberg, New York,1999, ISBN 3-540-64946-8, pages 42 to 63.

The main processes used in the production of synthetic leather are thedirect coating process, the transfer coating process (indirect coating)and the coagulation (wet) process. In contrast to the direct process,the coating in the transfer process is applied to a temporary supportwith a subsequent lamination step, in which the film is combined withthe textile substrate and detached from the temporary support (releasepaper). The transfer process is preferably employed with textilesubstrates, which do not permit high tensile stresses during coating, orwith open fabrics which are not particularly dense.

In the coagulation process, a textile substrate is usually coated with asolution comprising polyurethane in DMF. In a second step, the coatedsubstrate is passed through DMF/water baths, where the proportion ofwater is increased stepwise. Precipitation of the polyurethane andformation of a microporous film occur here. Use is made here of the factthat DMF and water have excellent miscibility and DMF and water serve asa solvent/non-solvent pair for polyurethane. Coagulated polyurethanecoatings are employed, in particular, for high-quality syntheticleather, since they have comparatively good breathing activity and aleather feel. The basic principle of the coagulation process is based onthe use of a suitable solvent/non-solvent pair for polyurethane. Thegreat advantage of the coagulation process is that microporous,breathing-active synthetic leather having an excellent leather feel canbe obtained. Examples are, for example, the synthetic leather brandsClarino® and Alcantara®. A disadvantage of the coagulation process isthe necessity to use large amounts of DMF as an organic solvent. Inorder to minimize the exposure of employees to DMF emissions duringproduction, additional design measures have to be taken, which representa not inconsiderable increased outlay compared with simpler processes.Furthermore, it is necessary to dispose of or work up large amounts ofDMF/water mixtures. This is problematical since water and DMF form anazeotrope and can therefore only be separated by distillation withincreased effort.

One object of the present invention was therefore to develop a processfor the coating of textile substrates which still enables coatedtextiles having good properties, such as, for example, good feel, to beobtained without the need to employ toxicologically unacceptablesolvents, such as, for example, DMF.

The object has been achieved by a process for the production of coatedtextiles, comprising at least the steps of

a) bringing a textile substrate into contact with an aqueous dispersionA comprising at least one inorganic salt and at least one modifiedcellulose,b) bringing a textile substrate into contact with an aqueous dispersionB comprising polyurethane andc) precipitation of the polyurethane in or on the textile substrate.

In step a), a textile substrate is brought into contact with an aqueoussolution comprising at least one inorganic salt and at least onemodified cellulose.

The inorganic salt is preferably a salt selected from the groupcomprising alkali metal salts and alkaline-earth metal salts. Theinorganic salt is particularly preferably a salt selected from the groupconsisting of alkali metal halides, alkali metal phosphates, alkalimetal nitrates, alkali metal sulfates, alkali metal carbonates, alkalimetal hydrogen carbonates, alkaline-earth metal halides, alkaline-earthmetal nitrates, alkaline-earth metal phosphates, alkaline-earth metalsulfates, alkaline-earth metal carbonates and alkaline-earth metalhydrogen carbonates. The inorganic salt is very particularly preferablysodium chloride, potassium chloride, sodium sulfate, sodium carbonate,potassium sulfate, potassium carbonate, sodium hydrogen carbonate,potassium hydrogen carbonate, magnesium chloride, magnesium sulfate,magnesium nitrate, calcium chloride, calcium nitrate or calcium sulfate.The inorganic salt is even more preferably calcium nitrate, magnesiumnitrate, calcium chloride or magnesium chloride.

The inorganic salt is preferably present in dispersion A in an amount of0.01 to 25% by weight, particularly preferably in an amount of 0.5 to15% by weight, and very particularly preferably in an amount of 0.5 to10% by weight, based on the total amount of dispersion A.

The chemically modified cellulose is preferably a compound selected fromthe group consisting of alkylated celluloses, hydroxyalkylatedcelluloses and carboxyalkylated celluloses.

The chemically modified cellulose is particularly preferably a compoundselected from the group consisting of methylcellulose, ethylcellulose,propylcellulose, hydroxymethylcellulose, hydroxyethylcellulose,hydroxymethylcellulose, hydroxypropylmethylcellulose,carboxymethylcellulose, carboxyethylcellulose andcarboxypropylcellulose.

The chemically modified cellulose is very particularly preferablymethylcellulose or ethylcellulose.

The modified cellulose is preferably present in dispersion A in anamount of 10 ppm to 5% by weight, particularly preferably in an amountof 100 ppm to 3% by weight, very particularly preferably in an amount of400 ppm to 1.5% by weight, based on the total amount of dispersion A.

The textile substrate is preferably brought into contact with an aqueousdispersion A at room temperature for a period of 2 to 4 minutes,particularly preferably 1 to 2 minutes, very particularly preferably 0.2to 1 minute. For the purposes of the present invention, bringing intocontact means partial or complete immersion, preferably completeimmersion, in a dispersion or application of the dispersion by means ofa hand coater, printing or spraying.

After being brought into contact with a dispersion A, the textilesubstrate is preferably passed through a wringer device consisting oftwo rollers in order to remove the excess dispersion A. The wringerdevice here should preferably be set in such a way that dispersion Aremains in the textile substrate in an amount of 60 to 180% by weight,particularly preferably 70 to 140%, very particularly preferably 80 to120%, based on the weight per unit area of the substrate (liquoruptake), before the substrate is brought into contact with a dispersionB containing polyurethane. The textile substrate is preferably partiallydried for a period of 2 to 10 minutes, particularly preferably 1 to 5minutes, using air, infrared or hot cylinders before it can be broughtinto contact with a dispersion B containing polyurethane.

The polyurethane present in dispersion B is not particularly restrictedso long as it is soluble in water, the term “polyurethane” alsoencompassing polyurethane-polyureas. A review of polyurethane (PUR)dispersions and processes therefor can be found in Rosthauser &Nachtkamp, “Waterborne Polyurethanes, Advances in Urethane Science andTechnology”, Vol. 10, pages 121-162 (1987). Suitable dispersions arealso described, for example, in “Kunststoff-handbuch” [PlasticsHandbook], Vol. 7, 2nd Edition, Hauser, pages 24 to 26.

Constituent components of dispersions B used in accordance with theinvention may be the following:

1) Organic di- and/or polyisocyanates, such as, for example,tetramethylene diisocyanate, hexamethylene diisocyanate (HDI),2-methylpentamethylene diisocyanate, 2,2,4-trimethylhexamethylenediisocyanate (THDI), dodecanemethylene diisocyanate,1,4-diisocyanatocyclohexane,3-isocyanatomethyl-3,3,5-trimethylcyclohexyl isocyanate (isophoronediisocyanate=IPDI), 4,4′-diisocyanatodicyclohexylmethane (Desmodur® W),4,4′-diisocyanato-3,3′-dimethyldicyclohexylmethane,4,4′-diisocyanato-2,2-dicyclohexylpropane, 1,4-diisocyanatobenzene, 2,4-or 2,6-diisocyanatotoluene or mixtures of these isomers, 4,4′-, 2,4- or2,2′-diisocyanatodiphenylmethane or mixtures of these isomers, 4,4-,2,4′- or 2,2′-diisocyanato-2,2-diphenylpropane-p-xylene diisocyanate andα,α,α′,α′-tetramethyl-m- or -p-xylene diisocyanate (TMXDI), and mixturesconsisting of these compounds. For the purposes of modification, smallamounts of trimers, urethanes, biurets, allophanates or uretdiones ofthe above-mentioned diisocyanates can be used. MDI, Desmodur W, HDIand/or IPDI are particularly preferred.2) Polyhydroxyl compounds having 1 to 8, preferably 1.7 to 3.5 hydroxylgroups per molecule and an (average) molecular weight of up to 16,000,preferably up to 4000. Low-molecular-weight polyhydroxyl compoundsdefined in each case, such as, for example, ethylene glycol, 1,2-,1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol,trimethylolpropane, glycerol, the product of the reaction of 1hydrazine+2 propylene glycol and oligomeric or polymeric hydroxylcompounds having molecular weights of 350 to 10,000, preferably 840 to3000, can be considered.

Relatively high-molecular-weight hydroxyl compounds includehydroxypolyesters, hydroxypolyethers, hydroxypolythioethers,hydroxypolyacetates, hydroxypolycarbonates and/or hydroxypolyesteramides which are known per se in polyurethane chemistry, preferablythose having average molecular weights of 350 to 4000, particularlypreferably those having average molecular weights of 840 to 3000.Hydroxypolycarbonates and/or hydroxypolyethers are particularlypreferred. When they are used, coagulates having particular stability tohydrolysis can be prepared.

3a) Ionic or potentially ionic hydrophilizing agents containing an acidgroup and/or an acid group in salt form and at least oneisocyanate-reactive group, for example an OH or NH₂ group. Examples arethe Na salt of ethylenediamine-β-ethylsulfonic acid (AAS salt solution),dimethylolpropionic acid (DMPA), dimethylolbutyric acid, hydroxypivalicacid or adducts of 1 mol of diamine, preferably isophoronediamine, and 1mol of an α,β-unsaturated carboxylic acid, preferably acrylic acid.3b) Nonionic hydrophilizing agents in the form of mono- and/ordifunctional polyethylene oxide or polyethylene-propylene oxide alcoholshaving molecular weights of 300 to 5000. Particular preference is givento monohydroxyl-functional ethylene oxide/propylene oxide polyethersbased on n-butanol having 35 to 85% by weight of ethylene oxide unitsand molecular weights of 900 to 2500. A content of at least 3% byweight, in particular at least 6% by weight, of nonionic hydrophilizingagents is preferred.4) Blocking agents for isocyanate groups, such as, for example, oximes(acetone oxime, butanone oxime or cyclohexanone oxime), secondary amines(diisopropylamine, dicyclohexylamine), NH-acidic heterocyclic substances(3,5-dimethylpyrazole, imidazole, 1,2,4-triazole), CH-acidic esters(C₁₋₄-alkyl malonates, acetic acid esters) or lactams (ε-caprolactam).Butanone oxime, diisopropylamine and 1,2,4-triazole are particularlypreferred.5) Polyamines as built-in chain extenders. These include, for example,the polyamines discussed under 6). The diamino-functional hydrophilizingagents discussed under 3a) are also suitable as chain extenders to beincorporated.6) Polyamine crosslinking agents. These are preferably aliphatic orcycloaliphatic diamines, although it is also possible, if needed, to usetrifunctional polyamines or polyfunctional polyamines in order toachieve specific properties. In general, it is possible to usepolyamines containing additional functional groups, such as, forexample, OH groups. The polyamine crosslinking agents, which are notincorporated into the polymer backbone at normal or slightly elevatedambient temperatures, for example 20 to 60° C., are either admixedimmediately during preparation of the reactive dispersions or at asubsequent point in time. Examples of suitable aliphatic polyamines areethylenediamine, 1,2- and 1,3-propylenediamine,1,4-tetramethylenediamine, 1,6-hexamethylenediamine, the isomer mixtureof 2,2,4- and 2,4,4-trimethylhexamethylenediamine,2-methylpentamethylenediamine and diethylenetriamine.

In a further preferred embodiment, dispersion B comprises at least onecoagulant besides polyurethane. A coagulant is a salt or acid, forexample ammonium salts of organic acids, which causes coagulation of thepolyurethane under certain conditions, such as, for example, aparticular temperature. These substances include an acid-generatingchemical agent, i.e. a substance which is not an acid at roomtemperature, but becomes an acid after warming. Certain examples of suchcompounds include ethylene glycol diacetate, ethylene glycol formate,diethylene glycol formate, triethyl citrate, monostearyl citrate and anorganic acid ester.

The coagulant is preferably present in the composition in an amount of 1to 10% by weight, based on the solids content of dispersion B.

The polyurethane present in dispersion B is preferably an anionic and/ornonionic hydrophilized polyurethane, which is obtainable by

A) the preparation of isocyanate-functional prepolymers from

-   -   A1) organic polyisocyanates    -   A2) polymeric polyols having number average molecular weights of        400 to 8000 g/mol, preferably 400 to 6000 g/mol and particularly        preferably 600 to 3000 g/mol, and OH functionalities of 1.5 to        6, preferably 1.8 to 3, particularly preferably 1.9 to 2.1, and    -   A3) optionally hydroxyl-functional compounds having molecular        weights of 32 to 400 g/mol and    -   A4) optionally isocyanate-reactive, anionic or potentially        anionic and/or optionally nonionic hydrophilizing agents,        B) subsequent reaction of all or some of the free NCO groups        thereof    -   B1) optionally with amino-functional compounds having molecular        weights of 32 to 400 g/mol and/or    -   B2) isocyanate-reactive, preferably amino-functional, anionic or        potentially anionic hydrophilizing agents        with chain extension, and dispersion of the resultant        prepolymers in water before, during or after step B), where any        potentially ionic groups present are converted into the ionic        form by partial or complete reaction with a neutralizer.

In order to achieve anionic hydrophilization, it is necessary to carryout A4) and/or B2) using hydrophilizing agents which contain at leastone group which is reactive to NCO groups, such as amino, hydroxyl orthiol groups, and in addition contain —COO⁻ or —SO₃ ⁻ or —PO₃ ²⁻ asanionic groups or fully or partially protonated acid forms thereof aspotentially anionic groups.

Preferred aqueous, anionic polyurethane dispersions (I) have a lowdegree of hydrophilic anionic groups, preferably 0.1 to 15milliequivalents per 100 g of solid resin.

In order to achieve good sedimentation stability, the number averageparticle size of the specific polyurethane dispersions is preferablyless than 750 nm, particularly preferably less than 500 nm and veryparticularly preferably less than 400 nm, determined by means of lasercorrelation spectroscopy.

The ratio of NCO groups in the compounds of component A1) toNCO-reactive groups, such as amino, hydroxyl or thiol groups, in thecompounds of components A2) to A4) during preparation of theNCO-functional prepolymer is 1.05 to 3.5, preferably 1.2 to 3.0,particularly preferably 1.3 to 2.5.

The amino-functional compounds in step B) are employed in such an amountthat the equivalent ratio of isocyanate-reactive amino groups in thesecompounds to the free isocyanate groups in the prepolymer is 40 to 150%,preferably between 50 and 125%, particularly preferably between 60 and120%.

Suitable polyisocyanates of component A1) are the aromatic, araliphatic,aliphatic or cycloaliphatic polyisocyanates having an NCO functionalityof 2 which are known per se to the person skilled in the art.

Examples of suitable polyisocyanates of this type are 1,4-butylenediisocyanate, 1,6-hexamethylene diisocyanate (HDI), isophoronediisocyanate (IPDI), 2,2,4- and/or 2,4,4-trimethylhexamethylenediisocyanate, the isomeric bis(4,4′-isocyanatocyclohexyl)methanes ormixtures thereof with any desired isomer content, 1,4-cyclohexylenediisocyanate, 1,4-phenylene diisocyanate, 2,4- and/or 2,6-tolylenediisocyanate, 1,5-naphthylene diisocyanate, 2,2′- and/or 2,4′- and/or4,4′-diphenylmethane diisocyanate, 1,3- and/or1,4-bis(2-isocyanatoprop-2-yl)-benzene (TMXDI),1,3-bis(isocyanatomethyl)benzene (XDI), and alkyl2,6-diisocyanato-hexanoates (lysine diisocyanates) containingC₁-C₈-alkyl groups.

Besides the above-mentioned polyisocyanates, it is also possible toemploy proportionately modified diisocyanates having a uretdione,isocyanurate, urethane, allophanate, biuret, iminooxadiazinedione and/oroxadiazinetrione structure and unmodified polyisocyanates containingmore than 2 NCO groups per molecule, for example4-isocyanatomethyloctane 1,8-diisocyanate (nonan triisocyanate) ortriphenylmethane 4,4′,4″-triisocyanate.

These are preferably polyisocyanates or polyisocyanate mixtures of theabove-mentioned type containing exclusively aliphatically and/orcycloaliphatically bonded isocyanate groups and having an average NCOfunctionality of the mixture of 2 to 4, preferably 2 to 2.6 andparticularly preferably 2 to 2.4.

1,6-Hexamethylene diisocyanate, isophorone diisocyanate, the isomericbis(4,4′-isocyanatocyclohexyl)methanes, and mixtures thereof, areparticularly preferably employed in A1).

Polymeric polyols having a number average molecular weight M_(n) of 400to 8000 g/mol, preferably 400 to 6000 g/mol and particularly preferably600 to 3000 g/mol, are employed in A2). These preferably have an OHfunctionality of 1.5 to 6, particularly preferably 1.8 to 3, veryparticularly preferably 1.9 to 2.1.

Polymeric polyols of this type are the polyester polyols, polyacrylatepolyols, polyurethane polyols, polycarbonate polyols, polyether polyols,polyester polyacrylate polyols, polyurethane polyacrylate polyols,polyurethane polyester polyols, polyurethane polyether polyols,polyurethane polycarbonate polyols and polyester polycarbonate polyolsknown per se in polyurethane coating technology. They can be employedindividually or in any desired mixtures with one another in A2).

Polyester polyols of this type are the polycondensates, known per se, ofdi- and optionally tri- and tetraols and di- and optionally tri- andtetracarboxylic acids or hydroxycarboxylic acids or lactones. Instead ofthe free polycarboxylic acids, it is also possible to use thecorresponding polycarboxylic anhydrides or correspondingpolycarboxylates of lower alcohols for the preparation of thepolyesters.

Examples of suitable diols are ethylene glycol, butylene glycol,diethylene glycol, triethylene glycol, polyalkylene glycols, such aspolyethylene glycol, furthermore 1,2-propanediol, 1,3-propanediol,1,3-butanediol, 1,4-butanediol, 1,6-hexanediol and isomers, neopentylglycol or neopentyl glycol hydroxypivalate, where 1,6-hexanediol andisomers, neopentyl glycol and neopentyl glycol hydroxypivalate arepreferred. In addition, it is also possible to employ polyols, such astrimethylolpropane, glycerol, erythritol, pentaerythritol,trimethylolbenzene or trishydroxyethyl isocyanurate.

Dicarboxylic acids which can be employed are phthalic acid, isophthalicacid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalicacid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid, sebacicacid, glutaric acid, tetrachlorophthalic acid, maleic acid, fumaricacid, itaconic acid, malonic acid, suberic acid, 2-methylsuccinic acid,3,3-diethylglutaric acid and/or 2,2-dimethylsuccinic acid. Thecorresponding anhydrides can also be used as acid source.

So long as the average functionality of the polyol to be esterifiedis >2, monocarboxylic acids, such as benzoic acid and hexanecarboxylicacid, can also be used in addition.

Preferred acids are aliphatic or aromatic acids of the above-mentionedtype. Particular preference is given to adipic acid, isophthalic acidand optionally trimellitic acid.

Hydroxycarboxylic acids which can be used concomitantly as reactionparticipants in the preparation of a polyester polyol containingterminal hydroxyl groups are, for example, hydroxycaproic acid,hydroxybutyric acid, hydroxydecanoic acid, hydroxystearic acid and thelike. Suitable lactones are caprolactone, butyrolactone and homologs.Caprolactone is preferred.

Hydroxyl-containing polycarbonates, preferably polycarbonate diols,having number average molecular weights M_(n) of 400 to 8000 g/mol,preferably 600 to 3000 g/mol, can likewise be employed in A2). These areobtainable by reaction of carbonic acid derivatives, such as diphenylcarbonate, dimethyl carbonate or phosgene, with polyols, preferablydiols.

Examples of diols of this type are ethylene glycol, 1,2- and1,3-propanediol, 1,3- and 1,4-butanediol, 1,6-hexanediol,1,8-octanediol, neopentyl glycol, 1,4-bishydroxymethylcyclohexane,2-methyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, dipropyleneglycol, polypropylene glycols, dibutylene glycol, polybutylene glycols,bisphenol A and lactone-modified diols of the above-mentioned type.

The polycarbonate diol preferably comprises 40 to 100% by weight ofhexanediol, preferably 1,6-hexanediol, and/or hexanediol derivatives.Hexanediol derivatives of this type are based on hexanediol and, besidesterminal OH groups, contain ester or ether groups. Derivatives of thistype are obtainable by reaction of hexanediol with excess caprolactoneor by etherification of hexanediol with itself to give di- ortrihexylene glycol.

Instead of or in addition to pure polycarbonate diols, it is alsopossible to employ polyether polycarbonate diols in A2).

The hydroxyl-containing polycarbonates preferably have a linearstructure.

Polyether polyols can likewise be employed in A2).

Suitable polyether polyols are, for example, the polytetramethyleneglycol polyethers known per se in polyurethane chemistry, as obtainableby polymerization of tetrahydrofuran by means of cationic ring opening.

Likewise suitable polyether polyols are the products, known per se, ofthe addition of styrene oxide, ethylene oxide, propylene oxide, butyleneoxides and/or epichlorohydrin onto di- or polyfunctional startermolecules. Polyether polyols based on the at least proportionateaddition of ethylene oxide onto di- or polyfunctional starter moleculescan also be employed as component A4) (nonionic hydrophilizing agents).

Suitable starter molecules which can be employed are all compounds knownfrom the prior art, such as, for example, water, butyl diglycol,glycerol, diethylene glycol, trimethylolpropane, propylene glycol,sorbitol, ethylenediamine, triethanolamine, 1,4-butanediol. Preferredstarter molecules are water, ethylene glycol, propylene glycol,1,4-butanediol, diethylene glycol and butyl diglycol.

Particularly preferred embodiments of the polyurethane dispersions (I)comprise, as component A2), a mixture of polycarbonate polyols andpolytetramethylene glycol polyols, where the proportion of polycarbonatepolyols in this mixture is 20 to 80% by weight and the proportion ofpolytetramethylene glycol polyols is 80 to 20% by weight. A proportionof 30 to 75% by weight of polytetramethylene glycol polyols and aproportion of 25 to 70% by weight of polycarbonate polyols arepreferred. A proportion of 35 to 70% by weight of polytetramethyleneglycol polyols and a proportion of 30 to 65% by weight of polycarbonatepolyols are particularly preferred, in each case with the proviso thatthe sum of the percent by weight of the polycarbonate polyols andpolytetramethylene glycol polyols is 100% and the proportion of the sumof the polycarbonate polyols and polytetramethylene glycol polyetherpolyols in component A2) is at least 50% by weight, preferably 60% byweight and particularly preferably at least 70% by weight.

The compounds of component A3) have molecular weights of 62 to 400g/mol.

Polyols in the said molecular weight range having up to 20 carbon atoms,such as ethylene glycol, diethylene glycol, triethylene glycol,1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butylene glycol,cyclohexanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, neopentylglycol, hydroquinone dihydroxyethyl ether, bisphenol A(2,2-bis(4-hydroxyphenyl)propane), hydrogenated bisphenol A(2,2-bis(4-hydroxycyclohexyl)propane), trimethylolpropane, glycerol,pentaerythritol, and any desired mixtures thereof with one another, canbe employed in A3).

Also suitable are ester diols in the said molecular weight range, suchas α-hydroxybutyl-ε-hydroxycaproic acid esters,ω-hydroxyhexyl-γ-hydroxybutyric acid esters, β-hydroxyethyl adipate orβ-hydroxyethyl terephthalate.

Furthermore, monofunctional, isocyanate-reactive, hydroxyl-containingcompounds can also be employed in A3). Examples of monofunctionalcompounds of this type are ethanol, n-butanol, ethylene glycol monobutylether, diethylene glycol monomethyl ether, ethylene glycol monobutylether, diethylene glycol monobutyl ether, propylene glycol monomethylether, dipropylene glycol monomethyl ether, tripropylene glycolmonomethyl ether, dipropylene glycol monopropyl ether, propylene glycolmonobutyl ether, dipropylene glycol monobutyl ether, tripropylene glycolmonobutyl ether, 2-ethylhexanol, 1-octanol, 1-dodecanol, 1-hexadecanol.

Preferred compounds of component A3) are 1,6-hexanediol, 1,4-butanediol,neopentyl glycol and trimethylolpropane.

Anionically or potentially anionically hydrophilizing compounds ofcomponent A4) are taken to mean all compounds which contain at least oneisocyanate-reactive group, such as a hydroxyl group, and at least onefunctionality, such as, for example, —COO⁻M⁺, —SO₃ ⁻M⁺, —PO(O⁻M⁺)₂,where M⁺ is, for example, a metal cation, H⁺, NH₄ ⁺, NHR₃ ⁺, where R mayin each case be a C₁-C₁₂-alkyl, C₅-C₆-cycloalkyl and/orC₂-C₄-hydroxyalkyl radical, which enters into a pH-dependentdissociation equilibrium on interaction with aqueous media and may inthis way be negatively charged or neutral. Suitable anionically orpotentially anionically hydrophilizing compounds are mono- anddihydroxycarboxylic acids, mono- and dihydroxysulfonic acids, and mono-and dihydroxyphosphonic acids, and salts thereof. Examples of anionic orpotentially anionic hydrophilizing agents of this type aredimethylolpropionic acid, dimethylolbutyric acid, hydroxypivalic acid,malic acid, citric acid, glycolic acid, lactic acid and the propoxylatedadduct of 2-butenediol and NaHSO₃, as described in DE-A 2 446 440, pages5-9, formulae I-III. Preferred anionic or potentially anionichydrophilizing agents of component A4) are those of the above-mentionedtype which contain carboxylate or carboxylic acid groups and/orsulfonate groups.

Particularly preferred anionic or potentially anionic hydrophilizingagents A4) are those which contain carboxylate or carboxylic acid groupsas ionic or potentially ionic groups, such as dimethylolpropionic acid,dimethylolbutyric acid and hydroxypivalic acid, or salts thereof.

Suitable nonionically hydrophilizing compounds of component A4) are, forexample, polyoxyalkylene ethers which contain at least one hydroxyl oramino group, preferably at least one hydroxyl group.

Examples are the monohydroxyl-functional polyalkylene oxide polyetheralcohols containing on statistical average 5 to 70, preferably 7 to 55ethylene oxide units per molecule, as are accessible in a manner knownper se by alkoxylation of suitable starter molecules (for example inUllmanns Encyclopadie der technischen Chemie [Ullmann's Encyclopedia ofIndustrial Chemistry], 4th Edition, Volume 19, Verlag Chemie, Weinheimpp. 31-38).

These are either pure polyethylene oxide ethers or mixed polyalkyleneoxide ethers, which contain at least 30 mol %, preferably at least 40mol %, based on all alkylene oxide units present, of ethylene oxideunits.

Particularly preferred nonionic compounds are monofunctional mixedpolyalkylene oxide polyethers which contain 40 to 100 mol % of ethyleneoxide units and 0 to 60 mol % of propylene oxide units.

Suitable starter molecules for nonionic hydrophilizing agents of thistype are saturated monoalcohols, such as methanol, ethanol, n-propanol,isopropanol, n-butanol, isobutanol, sec-butanol, the isomeric pentanols,hexanols, octanols and nonanols, n-decanol, n-dodecanol, n-tetradecanol,n-hexadecanol, n-octadecanol, cyclohexanol, the isomericmethylcyclohexanols or hydroxymethylcyclohexane,3-ethyl-3-hydroxymethyloxetane or tetrahydrofurfuryl alcohol, diethyleneglycol monoalkyl ethers, such as, for example, diethylene glycolmonobutyl ether, unsaturated alcohols, such as allyl alcohol,1,1-dimethylallyl alcohol or oleyl alcohol, aromatic alcohols, such asphenol, the isomeric cresols or methoxyphenols, araliphatic alcohols,such as benzyl alcohol, anisalcohol or cinnamyl alcohol, secondarymonoamines, such as dimethylamine, diethylamine, dipropylamine,diisopropylamine, dibutylamine, bis(2-ethylhexyl)amine, N-methyl- andN-ethylcyclohexylamine or dicyclohexylamine, and heterocyclic secondaryamines, such as morpholine, pyrrolidine, piperidine or 1H-pyrazole.Preferred starter molecules are saturated monoalcohols of theabove-mentioned type. Diethylene glycol monobutyl ether or n-butanol isparticularly preferably used as starter molecule.

Alkylene oxides which are suitable for the alkoxylation reaction are, inparticular, ethylene oxide and propylene oxide, which can be employed inany desired sequence or also as a mixture in the alkoxylation reaction.

Di- or polyamines, such as 1,2-ethylenediamine, 1,2- and1,3-diaminopropane, 1,4-diaminobutane, 1,6-diaminohexane,isophoronediamine, isomer mixture of 2,2,4- and2,4,4-trimethylhexamethylenediamine, 2-methylpentamethylenediamine,diethylenetriamine, triaminononane, 1,3- and 1,4-xylylenediamine,α,α,α′,α′-tetramethyl-1,3- and -1,4-xylylenediamine and4,4-diaminodicyclohexylmethane and/or dimethylethylenediamine, can beemployed as component B1). It is likewise possible to use hydrazine orhydrazides, such as adipohydrazide. Preference is given toisophoronediamine, 1,2-ethylenediamine, 1,4-diaminobutane, hydrazine anddiethylenetriamine.

In addition, compounds which, besides a primary amino group, alsocontain secondary amino groups or, besides an amino group (primary orsecondary), also contain OH groups can also be employed as componentB1). Examples thereof are primary/secondary amines, such asdiethanolamine, 3-amino-1-methylaminopropane,3-amino-1-ethylaminopropane, 3-amino-1-cyclohexylaminopropane,3-amino-1-methylaminobutane, alkanolamines, such asN-amino-ethylethanolamine, ethanolamine, 3-aminopropanol,neopentanolamine.

Furthermore, monofunctional isocyanate-reactive amino compounds, suchas, for example, methylamine, ethylamine, propylamine, butylamine,octylamine, laurylamine, stearylamine, isononyloxypropylamine,dimethylamine, diethylamine, dipropylamine, dibutylamine,N-methylaminopropylamine, diethyl(methyl)aminopropylamine, morpholine,piperidine, or suitable substituted derivatives thereof, amidoaminesmade from diprimary amines and monocarboxylic acids, monoketimes ofdiprimary amines, primary/tertiary amines, such asN,N-dimethylaminopropylamine, can also be employed as component B1).

Preferred compounds of component B1) are 1,2-ethylenediamine,1,4-diaminobutane and isophoronediamine.

Anionically or potentially anionically hydrophilizing compounds ofcomponent B2) are taken to mean all compounds which contain at least oneisocyanate-reactive group, preferably an amino group, and at least onefunctionality, such as, for example, —COO⁻M⁺, —SO₃ ⁻M⁺, —PO(O⁻M⁺)₂,where M⁺ is, for example, a metal cation, H⁺, NH₄ ⁺, NHR₃ ⁺, where R mayin each case be a C₁-C₁₂-alkyl radical, C₅-C₆-cycloalkyl radical and/orC₂-C₄-hydroxyalkyl radical, which enters into a pH-dependentdissociation equilibrium on interaction with aqueous media and may inthis way be negatively charged or neutral.

Suitable anionically or potentially anionically hydrophilizing compoundsare mono- and diaminocarboxylic acids, mono- and diaminosulfonic acidsand mono- and diaminophosphonic acids, and salts thereof. Examples ofanionic or potentially anionic hydrophilizing agents of this type areN-(2-aminoethyl)-β-alanine, 2-(2-aminoethylamino)-ethanesulfonic acid,ethylenediaminepropyl- or -butylsulfonic acid, 1,2- or1,3-propylenediamine-β-ethyl-sulfonic acid, glycine, alanine, taurine,lysine, 3,5-diaminobenzoic acid and the product of the addition reactionof IPDA and acrylic acid (EP-A 0 916 647, Example 1). Furthermore,cyclohexylaminopropanesulfonic acid (CAPA), which is known from WO-A01/88006, can be used as an anionic or potentially anionichydrophilizing agent.

Preferred anionic or potentially anionic hydrophilizing agents ofcomponent B2) are those of the above-mentioned type which containcarboxylate or carboxylic acid groups and/or sulfonate groups, such asthe salts of N-(2-aminoethyl)-β-alanine, of2-(2-aminoethylamino)ethanesulfonic acid or of the product of theaddition reaction of IPDA and acrylic acid (EP-A 0 916 647, Example 1).

The hydrophilization can also be carried out using mixtures of anionicor potentially anionic hydrophilizing agents and nonionic hydrophilizingagents.

In a preferred embodiment for the preparation of the specificpolyurethane dispersions, components A1) to A4) and B1) to B2) areemployed in the following amounts, where the individual amounts alwaysadd up to 100% by weight:

5 to 40% by weight of component A1),55 to 90% by weight of A2),0.5 to 20% by weight of the sum of components A3) and B1),0.1 to 25% by weight of the sum of components A4) and B2), where 0.1 to5% by weight of anionic or potentially anionic hydrophilizing agentsfrom A4) and/or B2) are used, based on the total amounts of componentsA1) to A4) and B1) to B2).

In a particularly preferred embodiment for the preparation of thespecific polyurethane dispersions, components A1) to A4) and B1) to B2)are employed in the following amounts, where the individual amountsalways add up to 100% by weight:

5 to 35% by weight of component A1),60 to 90% by weight of A2),0.5 to 15% by weight of the sum of components A3) and B1),0.1 to 15% by weight of the sum of components A4) and B2), where 0.2 to4% by weight of anionic or potentially anionic hydrophilizing agentsfrom A4) and/or B2) are used, based on the total amounts of componentsA1) to A4) and B1) to B2).

In a very particularly preferred embodiment for the preparation of thespecific polyurethane dispersions, components A1) to A4) and B1) to B2)are employed in the following amounts, where the individual amountsalways add up to 100% by weight:

10 to 30% by weight of component A1),65 to 85% by weight of A2),0.5 to 14% by weight of the sum of components A3) and B1),0.1 to 13.5% by weight of the sum of components A4) and B2), where 0.5to 3.0% by weight of anionic or potentially anionic hydrophilizingagents from A4) and/or B2) are used, based on the total amounts ofcomponents A1) to A4) and B1) to B2).

The preparation of the anionically hydrophilized polyurethanedispersions (I) can be carried out in one or more steps in a homogeneousor multistep reaction, some in the disperse phase. After complete orpartial polyaddition from A1) to A4), a dispersion, emulsification ordissolution step is carried out. If desired, a further polyaddition ormodification in the disperse phase is subsequently carried out.

All processes known from the prior art, such as, for example, theprepolymer mixing process, acetone process or melt dispersal process,can be used here. The acetone process is preferably used.

For preparation by the acetone process, all or some of constituents A2)to A4) and the polyisocyanate component A1) are usually initiallyintroduced for the preparation of an isocyanate-functional polyurethaneprepolymer and optionally diluted with a solvent which is miscible withwater, but inert to isocyanate groups and heated to temperatures in therange from 50 to 120° C. In order to accelerate the isocyanate additionreaction, the catalysts known in polyurethane chemistry can be employed.

Suitable solvents are the conventional aliphatic, keto-functionalsolvents, such as acetone, 2-butanone, which can be added not only atthe beginning of the preparation, but, if desired, can also partly beadded later. Preference is given to acetone and 2-butanone.

Other solvents, such as xylene, toluene, cyclohexane, butyl acetate,methoxypropyl acetate, N-methylpyrrolidone, N-ethylpyrrolidone, solventscontaining ether or ester units, may additionally be employed anddistilled off in full or part or, in the case of N-methylpyrrolidone,N-ethylpyrrolidone, remain completely in the dispersion. However, othersolvents apart from the conventional aliphatic, keto-functional solventsare preferably not used.

Any constituents of A1) to A4) which have not yet been added at thebeginning of the reaction are subsequently metered in.

In the preparation of the polyurethane prepolymer from A1) to A4), themolar ratio of isocyanate groups to isocyanate-reactive groups is 1.05to 3.5, preferably 1.2 to 3.0, particularly preferably 1.3 to 2.5.

The conversion of components A1) to A4) into the prepolymer is carriedout in part or full, but preferably in full. Thus, polyurethaneprepolymers which contain free isocyanate groups are obtained in thesolid state or in solution.

In the neutralization step for the partial or complete conversion ofpotentially anionic groups into anionic groups, bases, such as tertiaryamines, for example trialkylamines having 1 to 12 C atoms, preferably 1to 6 C atoms, particularly preferably 2 to 3 C atoms, in each alkylradical or alkali metal bases, such as the corresponding hydroxides, areemployed.

Examples thereof are trimethylamine, triethylamine, methyldiethylamine,tripropylamine, N-methylmorpholine, methyldiisopropylamine,ethyldiisopropylamine and diisopropylethylamine. The alkyl radicals mayalso carry, for example, hydroxyl groups, as in the case of thedialkylmonoalkanolamines, alkyldialkanolamines and trialkanolamines.Neutralizers which can be employed, if desired, are also inorganicbases, such as aqueous ammonia solution or sodium hydroxide or potassiumhydroxide.

Preference is given to ammonia, triethylamine, triethanolamine,dimethylethanolamine or diisopropylethylamine, as well as sodiumhydroxide and potassium hydroxide, particularly preferably sodiumhydroxide and potassium hydroxide.

The molar amount of the bases is 50 to 125 mol %, preferably between 70and 100 mol %, of the molar amount of the acid groups to be neutralized.The neutralization can also be carried out simultaneously with thedispersion if the dispersion water already comprises the neutralizer.

In a further process step, the resultant prepolymer is subsequentlydissolved, if this has not already taken place or has only taken placein part, with the aid of aliphatic ketones, such as acetone or2-butanone.

In the chain extension in step B), NH₂— and/or NH-functional componentsare reacted in part or full with the remaining isocyanate groups of theprepolymer. The chain extension/termination is preferably carried outbefore the dispersion in water.

For the chain termination, amines B1) containing an isocyanate-reactivegroup, such as methylamine, ethylamine, propylamine, butylamine,octylamine, laurylamine, stearylamine, isononyloxypropylamine,dimethylamine, diethylamine, dipropylamine, dibutylamine,N-methylaminopropylamine, diethyl(methyl)aminopropylamine, morpholine,piperidine, or suitable substituted derivatives thereof, amidoaminesmade from diprimary amines and monocarboxylic acids, monoketimes ofdiprimary amines, primary/tertiary amines, such asN,N-dimethylaminopropylamine, are usually used.

If the partial or complete chain extension is carried out using anionicor potentially anionic hydrophilizing agents corresponding to definitionB2) containing NH₂ or NH groups, the chain extension of the prepolymersis preferably carried out before the dispersion.

The aminic components B1) and B2) can optionally be employed in water-or solvent-diluted form in the process according to the invention,individually or in mixtures, where any sequence of addition is inprinciple possible.

If water or organic solvents are used concomitantly as diluents, thediluent content in the component employed in B) for chain extension ispreferably 70 to 95% by weight.

The dispersion is preferably carried out after the chain extension. Tothis end, the dissolved and chain-extended polyurethane polymer iseither introduced into the dispersion water, optionally with high shear,such as, for example, vigorous stirring, or conversely the dispersionwater is stirred into the chain-extended polyurethane polymer solutions.The water is preferably added to the dissolved chain-extendedpolyurethane polymer.

The solvent still present in the dispersions after the dispersion stepis usually subsequently removed by distillation. Removal during thedispersion is likewise possible.

The residual content of organic solvents in the polyurethane dispersions(I) is typically less than 1.0% by weight, based on the entiredispersion.

The pH of the polyurethane dispersions (I) which are essential to theinvention is typically less than 9.0, preferably less than 8.5,particularly preferably less than 8.0 and very particularly preferably6.0 to 7.5.

The solids content of the polyurethane dispersions (I) is 40 to 70% byweight, preferably 50 to 65% by weight, particularly preferably 55 to65% by weight.

In a further preferred embodiment, dispersion B likewise comprisescoagulants (II) besides anionically hydrophilized polyurethane.

Coagulants (II) which can be employed in the compositions are allorganic compounds containing at least 2 cationic groups, preferably allknown cationic flocculants and precipitants from the prior art, such ascationic homopolymers or copolymers of salts ofpoly[2-(N,N,N-trimethylamino)ethyl acrylate], of polyethyleneimine, ofpoly[N-(dimethylamino-methyl)-acrylamide], of substituted acrylamides,of substituted methacrylamides, of N-vinylformamide, ofN-vinylacetamide, of N-vinylimidazole, of 2-vinylpyridine or of4-vinylpyridine.

Preferred coagulants (II) are cationic copolymers of acrylamide whichcontain structural units of the general formula (2), particularlypreferably cationic copolymers of acrylamide which contain structuralunits of the formula (1) and those of the general formula (2):

where

R is C═O, —COO(CH₂)₂— or —COO(CH₂)₃— and

X⁻ is a halide ion, preferably chloride.

The cationic coagulant (II) employed is particularly preferably apolymer of this type having a number average molecular weight of 500,000to 50,000,000 g/mol.

Coagulants (II) of this type are marketed, for example, under the tradename Praestol® (Degussa Stockhausen, Krefeld, Del.) as flocculants forsewage sludges. Preferred coagulants of the Praestol® type are Praestol®K111L, K122L, K133L, BC 270L, K 144L, K 166L, BC 55L, 185K, 187K, 190K,K222L, K232L, K233L, K234L, K255L, K332L, K 333L, K 334L, E 125, E 150,and mixtures thereof. Very particularly preferred coagulants arePraestol® 185K, 187K and 190K, and mixtures thereof.

Dispersion B preferably comprises at least one pigment.

The manner in which the precipitation in or on the textile substrate isaccomplished depends to a large extent on the chemical composition ofthe dispersion B used in accordance with the invention and in particularon the type of coagulant, if present. For example, the precipitation canbe carried out by evaporation coagulation or by salt, acid orelectrolyte coagulation.

In general, the precipitation is achieved by an increase in temperature.For example, the textile substrate can be subjected to brief heattreatment with steam, for example at 100 to 110° C. for 1 to 10 s. Thisis particularly preferred if ammonium salts or organic acids are used ascoagulant. If, on the other hand, the above-mentioned acid-generatingchemicals are used as coagulant, the precipitation is preferably carriedout as described in U.S. Pat. No. 5,916,636, U.S. Pat. No. 5,968,597,U.S. Pat. No. 5,952,413 and U.S. Pat. No. 6,040,393.

Alternatively, the coagulation is caused by dipping into a saltsolution. The coagulation is preferably carried out using an inorganicsalt selected from the group consisting of alkali metal salts andalkaline-earth metal salts. The inorganic salt is particularlypreferably a salt selected from the group consisting of alkali metalhalides, alkali metal nitrates, alkali metal phosphates, alkali metalsulfates, alkali metal carbonates, alkali metal hydrogen carbonates,alkaline-earth metal halides, alkaline-earth metal phosphates,alkaline-earth metal nitrates, alkaline-earth metal sulfates,alkaline-earth metal carbonates and alkaline-earth metal hydrogencarbonates. The inorganic salt is very particularly preferably sodiumchloride, potassium chloride, sodium sulfate, sodium carbonate,potassium sulfate, potassium carbonate, sodium hydrogen carbonate,potassium hydrogen carbonate, magnesium chloride, magnesium sulfate,calcium chloride or calcium sulfate. The inorganic salt is still morepreferably calcium chloride or magnesium chloride.

The inorganic salt is preferably present in the salt solution in anamount of 1 to 25% by weight, particularly preferably in an amount of 1to 15% by weight, very particularly preferably in an amount of 1 to 10%by weight, based on the total amount of salt solution.

After the precipitation in step c), further steps, such as drying orcondensation, are carried out if necessary.

The textile substrate employed is preferably a woven fabric, knittedfabric or nonwoven based on natural and/or synthetic fibers. The textilesubstrate is particularly preferably a nonwoven (staple fiber nonwoven,microfiber nonwoven or the like).

The textile substrate can preferably be built up from fibers ofpolyester, nylon (6 or 6,6), cotton, polyester/cotton blends, wool,ramie, spandex, glass, thermoplastic polyurethane (TPU), thermoplasticolefins (TPO) or the like. The textile substrate can have alinked/mesh-like (knitted), woven or nonwoven construction.

The textile substrate can be treated with dyes, colorants, pigments, UVabsorbers, plasticizers, soil redeposition agents, lubricants,antioxidants, flame inhibitors, rheology agents and the like, eitherbefore coating or thereafter, but there is a preference for suchadditions before coating.

If a defined nonwoven fabric is impregnated with an elastomer polymerand coagulated, and a normal coloring process is subsequently carriedout, a suede-like synthetic leather having good color developmentproperties is obtained.

The present invention therefore furthermore relates to a coated textile,preferably synthetic leather, obtained by the process according to theinvention.

EXAMPLES

Dispersion A has the following composition:

Ca(NO₃)₂  80 pbw Methylcellulose  0.4 pbw Water 920 pbw

Dispersion B1 for salt coagulation has the following composition:

Impranil 1380 1000 pbw Water 5000 pbw

The process for the preparation of the coated textile using saltcoagualtion is described in FIG. 1.

Dispersion B2 for heat coagulation has the following composition:

Impranil DLU 100 pbw  Coagulant WS 20 pbw Emulvin WA 20 pbw Water 5000pbw 

The process for the preparation of the coated textile using heatcoagualtion is described in FIG. 2.

Substrates which have been subjected to the process without the bringinginto contact with dispersion A as described had a very hard and stifffeel. By contrast, substrates which were treated in accordance with theinvention exhibited a pleasantly soft, round feel. On subsequent coatingof the resultant substrates, considerable differences were likewiseapparent between the substrates treated with dispersion A and theuntreated substrates, such that the fall of the folds (folding) appearedsharp and/or blistered in the case of the untreated coagulant. Thesubstrate treated in accordance with the invention exhibited round,optically perfect folding.

1. Process for the production of coated textiles, comprising at leastthe steps of a) bringing a textile substrate into contact with anaqueous dispersion A comprising at least one inorganic salt and at leastone modified cellulose, b) bringing a textile substrate into contactwith an aqueous dispersion B comprising polyurethane and c)precipitation of the polyurethane in or on the textile substrate. 2.Process according to claim 1, where the inorganic salt is a saltselected from the group consisting of alkali metal salts andalkaline-earth metal salts.
 3. Process according to claim 2, where thealkali metal salt is a salt selected from the group consisting of alkalimetal halides, alkali metal nitrates, alkali metal phosphates, alkalimetal sulfates, alkali metal carbonates and alkali metal hydrogencarbonates.
 4. Process according to claim 2, where the alkaline-earthmetal salt is a salt selected from the group consisting ofalkaline-earth metal halides, alkaline-earth metal nitrates,alkaline-earth metal phosphates, alkaline-earth metal sulfates,alkaline-earth metal carbonates and alkaline-earth metal hydrogencarbonates.
 5. Process according to claim 1, where the inorganic salt ispresent in dispersion A in an amount of 0.01 to 25% by weight, based onthe total amount of dispersion A.
 6. Process according to claim 1, wherethe modified cellulose is a compound selected from the group consistingof methylcellulose, ethylcellulose, propylcellulose,hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose,hydroxy

propylmethylcellulose, carboxymethylcellulose, carboxyethylcellulose andcarboxy

propylcellulose.
 7. Process according to claim 1, where the modifiedcellulose is present in dispersion A in an amount of 10 ppm to 5% byweight, based on the total amount of dispersion A.
 8. Process accordingto claim 1, characterized in that the textile substrate employed is awoven fabric, knitted fabric or nonwoven based on natural and/orsynthetic fibers.
 9. Process according to claim 1, characterized in thatthe polyurethane is precipitated in step c) in a bath containing wateror on use of a temperature in the range from 80 to 120° C.
 10. Coatedtextile obtainable by a process according to claim
 1. 11. Coated textileaccording to claim 10, characterized in that the coated textile issynthetic leather.